Replace "stat struct" with "GStatBuf" and "stat" with "g_stat" where
appropriate to fix cross-platform issues, specifically on Windows.
Code should be identical on *nix but fixes some serious issues
on Windows:
- Field widths of "struct stat" are not constant on Windows.
If the stat function does not match the stat struct used
it will cause overwrites and undefined behavior
- The Windows stat function needs a properly encoded filename.
In many places we pass an UTF-8 encoded value which breaks as soon
as non-ASCII characters are involved.
https://bugzilla.gnome.org/show_bug.cgi?id=787772
303858fa76
